International Journal of Asian Social Science 2016, Vol. 6(7): pp418-429The prevalence of HIV/AIDS in Tanzania has slightly fallen from 5.7 in 2007/2008 to 5.1% in 2001/2012 for people aged between15-49. However, the epidemic’s severity differs from one location to another and from one population segment to another. Petty traders across the border are assumed to be at high risk of contracting the disease. This paper assessed risk behavior among petty traders across Namanga border of Tanzania and Kenya. Using 120 respondents, the paper adopted a cross-sectional research design to collect both quantitative and qualitative data. A well structured questionnaire and checklist of questions were used tools for data collection. The paper revealed that apart from having high knowledge on HIV/AIDS, a number of risk behaviors such as having multiple partners, non use of condoms and excessive consumption of alcohol were practiced by petty traders. Further, frequent contraction of sexual transmitted infections (STIs) other than HIV/AIDS was also reported to increased chances for HIV/AIDS infection. It was concluded that the struggle against poverty by the petty traders increases high risk of contracting STIs such as HIV/AIDS. It is recommended that the government through institutions such as Tanzania Commission for AIDS (TACAIDS) and other Non Government Organizations continue with the campaign against HIV/AIDS to specific group of communities including petty traders. The campaign should go hand in hand with training on life management skills among petty traders.